Abstract:

Purpose: Experimental evidence exists that cardiac action of dobutamine is mediated by alfa-1 and beta- adrenergic receptors. However, uncertainty remains regarding the vascular effect of dobutamine and contribution of beta-adrenergic receptors to this effect. The aim of the present study was to investigate the direct effect of dobutamine in the rat aorta and the role of beta-adrenergic receptors in this effect. Materials and methods: The isolated thoracic aortic rings were mounted in organ bath containing Krebs-Henseleit solution. After an equilibiration period, endothelial integrity was then checked by the response to acetylcholine (10 μM) in aortic rings pre-contracted with phenylephrine (1 μM). After washout, dobutamine (0.001-10 μM) was added to generate cumulative concentration–response curves (CCRCs). To investigate the role of alfa- and beta- adrenergic receptors in the dobutamine-induced vascular response, prazosin (0.0003 µM) or propranolol (1 µM) was added to the bath medium 30 min before the addition of dobutamine in some experiments.. Results: Dobutamine produced concentration-dependent contraction in the endothelium-intact isolated rat aorta. This effect was significantly inhibited by either propranolol or prazosin (p<0.05). Prazosin also significantly supressed the maximum vascular response obtained by dobutamine (p<0.05). Conclusion: The results, to the best of my knowledge, demonstrates for the first time that beta-adrenergic receptors are involved in the vasoconstrictor effect of dobutamine in the endothelium-intact rat aorta.

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